Question

The sum of deviations of n observations from 25 is 25 and sum of deviations of the same n observations from 35 is -25.find the mean of the observations

Answer 1

Let 'n' be the required number of observations
Therefore,
∑(Xi - 25) = 25
∑ Xi - 25n = 25 .....(i)
Similarly,
∑(Xi - 35)= -25
∑ Xi - 35n = -25......(ii)
On subtracting the both
∑ Xi - 25n =  25
∑ Xi - 35n = -25
(-)   (+)     (+)
-------------------------------------
10n=50n=5
Putting n in (i)
We get,
∑of Xi - 25(5) = 25 
∑ Xi - 125 = 25
∑ of Xi = 150 
Now mean is given by
x= ∑ Xi / n  = 150/5  = 30 (Ans)

Answer 2

here is your answer hope it's help